"Her kit is useless. Her utility is nonexistent."
That sounds like someone who has only played with idiots that don't know how to use her. Her biggest weakness is a lack of CC, but she has a hell of a lot of utility. In addition to having free low-cooldown escapes and engages that can be reused, she has synergy with Yasuo (seriously, nobody seems to expect the flash+unburrow, never mind normal E+unburrow). Her tunnels are actually a good alternate sort of warding--there's incentive to stomp them, but seeing them disappear or even start to be damaged indicates enemy presence.
As a lane champion, the tunnels and ult are excellent both for escaping ganks and for quickly returning to lane. They also allow for low-risk backdooring and dragons, &c, all the stuff that traditionally goes along with a walljump. She's like Jax and Irelia: enough inbuilt damage to build almost entirely tanky and still be really dangerous. Her burrowed passive vision is excellent not in and of itself, but because her team can see it. That singlehandedly shuts down the ability of Eve, Twitch, Talon, or Shaco to safely engage on any team that's paying attention.
That said, a lot of people are really bad with her, sort of like Gnar when he was released. One thing that needs changing is the burrowed Q -- personally I'd like to see them remove the damage and add a slow. I'd also like to see variable-length burrows (not necessarily longer ones, just the ability to make them shorter to hide in more bushes). She's also more meh in jungle, especially post-Devourer nerf. In lane she's much better off, getting a real sixth item, having minion vision to let her stay burrowed to watch for ganks, easy returns to lane, &c.
e: IDC, maybe it's just fun playing Rek'Sai in lane. Super-easy trading, manaless, inbuilt sustain and gank-detection, free summoner-teleport on a really low cooldown... :|